While Pinyin uses the Latin alphabet, it should be kept in mind that it represents the sounds of Mandarin, not of English or any other language. Other than to express tonality, the only letter with diacritics that is used is “ü”. It uses four different diacritics on vowels to represent tones: ā, á, ǎ, à. Some have used numbers to represent the tones, but this is no longer as necessary as it used to be, because many software tools have become available for typing Pinyin with diacritical tone marks, as preferred by the Pinyin standard.